Enhancing Mechanical Performance of High-Density Polyethylene at Different Environmental Conditions with Outstanding Foamability through In-Situ Rubber Nanofibrillation: Exploring the Impact of Interface Modification.

In this study, we utilized in situ nanofibrillation of thermoplastic polyester ether elastomer (TPEE) within a high-density polyethylene (HDPE) matrix to enhance the rheological properties, foamability, and mechanical characteristics of the HDPE nanocomposite at both room and subzero temperatures. Due to the inherent polarity differences between these two components, TPEE is thermodynamically incompatible with the nonpolar HDPE. To address this compatibility issue, we employed a compatibilizer, styrene/ethylene-butylene/styrene copolymer-grafted maleic anhydride (SEBS-g-MA), to reduce the interfacial tension between the two blend components. In the initial step, we prepared a 10% masterbatch of HDPE/TPEE with and without the compatibilizer using a twin-screw extruder. Subsequently, we processed the 10% masterbatch further through spun bonding to create fiber-in-fiber composites. Scanning electron microscopy (SEM) analysis revealed a significant reduction in the spherical size of HDPE/TPEE particles following the inclusion of SEBS-g-MA, as well as a much smaller TPEE nanofiber size (approximately 60-70 nm for 5% TPEE). Moreover, extensional rheological testing revealed a notable enhancement in extensional rheological properties, with strain-hardening behavior being more pronounced in the compatibilized nanofibrillar composites compared to the noncompatibilized ones. SEM images of the foam structures depicted substantial improvement in the foamability of HDPE in terms of the cell size and density following the nanofibrillation process and the use of the compatibilizer. Ultimately, the in situ rubber fibrillation and enhancement of HDPE and TPEE interface using a compatibilizer led to increasing the HDPE ductility at room and subzero temperatures while maintaining its stiffness.

Melamine Network as a Solution for Significant Enhancement of the Mechanical, Adsorptive, and Surface Properties in a Novel Carbon Nanomaterial-Silica Aerogel Composite.

Silica aerogels exhibit exceptional characteristics such as mesoporosity, light weight, high surface area, and pore volume. Nevertheless, their utilization in industrial settings remains constrained due to their brittleness, moisture sensitivity, and costly synthesis procedure. Several studies have proved that adding nanofillers, such as carbon nanotubes (CNT) or graphene nanoplatelets (GNP), can improve the mechanical strength of the aerogels. The incorporation of nanofillers is often accompanied by agglomeration and pore blockage, which, in turn, deteriorates the surface area, pore volume, and low density. Including flexible melamine foam (MF) as a scaffold for the silica aerogel and nanofiller composite can prevent the restacking of the nanofillers through π-π interaction, hence maintaining the incredible properties of aerogels and improving their mechanical properties. CNT, GNP, and the polymeric silica precursor, polyvinyltrimethoxysilane (PVTMS), were added to a MF, at varying concentrations, to fabricate the MF-aerogel nanocomposites. Surfactant and sonication were utilized to ensure a homogeneous dispersion of the nanofillers in the system. The presence of MF prevented the agglomeration of nanofillers, resulting in lower density and relatively higher surface properties (SBET up to 929 m2·g-1 and pore volume up to 4.34 cc·g-1). Moreover, the MF-supported samples could endure 80% strain without breakage and showed an outstanding compressive strength of up to ∼20 MPa. These aerogel nanocomposites also demonstrated an excellent volatile organic compound (∼2680 mg·g-1) and cationic dye adsorption (∼10 mg·g-1).

Two-dimensional MXene nanosheets on nano-scale fibrils in hierarchical porous structure to achieve ultra-high sensitivity.

The complex hybrid nanostructure combining a two-dimensional (2D) conductive material and a hierarchical nanoscale skeleton plays an important role to enhance its piezoresistive sensitivity. To construct such a novel hybrid nanostructure, a piezoresistive sensor was designed with the following strategy to take the full advantages of 2D MXene and nanoscale fibrils: ethylene oxide propylene oxide random copolymer (EOPO) was grafted to ethylene-vinyl alcohol (EVOH) molecular chains and was foamed by an environmentally-friendly supercritical CO2 (scCO2) foaming technology to fabricate abundant nanoscale EVOH fibrils surrounding micropores; MXene featured as a 2D structure of nanoscale size that strongly interacted with this hierarchical nanoscale skeleton, and MXene not only convolved on nanoscale fibrils to generate bumps but also MXene covered the end of broken fibrils to build spots, and furthermore, MXene adhered on the soft EOPO embedded EVOH fibrils to form wrinkles, in which these bumps, spots and wrinkles assembled by highly conductive 2D MXene offered sufficient contacts when the hierarchical nanoscale skeleton was compressed (these contacts would then destruct when the skeleton recovered). Such an elaborated hybrid nanostructural design exploits the full potential of 2D MXene and hence achieves an ultra-high sensitivity of 6895.0 kPa-1 for this fabricated MXene piezoresistive sensor.

Comparative Effects of Hydrazine and Thermal Reduction Methods on Electromagnetic Interference Shielding Characteristics in Foamed Titanium Carbonitride MXene Films.

The urgent need for the development of micro-thin shields against electromagnetic interference (EMI) has sparked interest in MXene materials owing to their metallic electrical conductivity and ease of film processing. Meanwhile, postprocessing treatments can potentially exert profound impacts on their shielding effectiveness (SE). This work comprehensively compares two reduction methods, hydrazine versus thermal, to fabricate foamed titanium carbonitride (Ti3CNTx) MXene films for efficient EMI shielding. Upon treatment of ≈ 100 µm-thick MXene films, gaseous transformations of oxygen-containing surface groups induce highly porous structures (up to ≈ 74.0% porosity). The controlled application of hydrazine and heat allows precise regulation of the reduction processes, enabling tailored control over the morphology, thickness, chemistry, and electrical properties of the MXene films. Accordingly, the EMI SE values are theoretically and experimentally determined. The treated MXene films exhibit significantly enhanced SE values compared to the pristine MXene film (≈ 52.2 dB), with ≈ 38% and ≈ 83% maximum improvements for the hydrazine and heat-treated samples, respectively. Particularly, heat treatment is more effective in terms of this enhancement such that an SE of 118.4 dB is achieved at 14.3 GHz, unprecedented for synthetic materials. Overall, the findings of this work hold significant practical implications for advancing high-performance, non-metallic EMI shielding materials.

Incorporating Loss Factor Modular Design for Full Ku-Band Microwave Attenuation in Double-Layered Graphene Aerogels.

The fabrication of absorption-dominant electromagnetic interference (EMI) shielding materials is a pressing priority to prevent secondary electromagnetic pollution in miniaturized electronic devices and communication systems. Meeting this goal has remained a tough challenge to keep pace with the rapid evolution of electronics due to the complex compositional and structural design and narrow operating bands. This work articulates a sound and simple strategy to precisely modulate the electrical conductivity of reduced graphene oxide (rGO), as the building block in lightweight double-layered rGO-film/rGO-aerogel/polyvinyl-alcohol (PVA) composites, for efficient microwave absorption over the entire Ku-band frequency range. These constructs reasonably comprised a porous absorption structure built from parallel rGO sheets aligned and prepared via freeze casting followed by freeze drying. The electrical conductivity and impedance of this layer were tuned by varying the annealing temperature from 400 to 800 °C, thereby adjusting the degree of reduction and the absorption characteristic. This layer was backed by a highly conductive rGO film reduced at a high temperature of 1000 °C, with a reflectivity of 97.5%. The incorporation of this film ensured high EMI shielding effectiveness of the double-layered structure through the absorption-reflection-reabsorption mechanism, consistent with the predicted values based on calculated loss factors and the input impedance of the structure. Accordingly, at an average EMI shielding effectiveness of 57.59 dB, the reflection shielding effectiveness (SER) and reflectivity (R) of the assembled composites were optimized to be as low as 0.22 dB and 0.049, respectively. This equates to approximately 99.999% shielding (SET) and ∼95% absorptivity (A) of the incident wave. This study opens new avenues for the development of lightweight (with a density as low as 15 mg/cm3) absorption-dominant EMI shielding composite materials with promising EMI shielding efficiency and potential applications in modern electronics.

Efficient Electromagnetic Wave Absorption and Thermal Infrared Stealth in PVTMS@MWCNT Nano-Aerogel via Abundant Nano-Sized Cavities and Attenuation Interfaces.

Pre-polymerized vinyl trimethoxy silane (PVTMS)@MWCNT nano-aerogel system was constructed via radical polymerization, sol-gel transition and supercritical CO2 drying. The fabricated organic-inorganic hybrid PVTMS@MWCNT aerogel structure shows nano-pore size (30-40 nm), high specific surface area (559 m2 g-1), high void fraction (91.7%) and enhanced mechanical property: (1) the nano-pore size is beneficial for efficiently blocking thermal conduction and thermal convection via Knudsen effect (beneficial for infrared (IR) stealth); (2) the heterogeneous interface was beneficial for IR reflection (beneficial for IR stealth) and MWCNT polarization loss (beneficial for electromagnetic wave (EMW) attenuation); (3) the high void fraction was beneficial for enhancing thermal insulation (beneficial for IR stealth) and EMW impedance match (beneficial for EMW attenuation). Guided by the above theoretical design strategy, PVTMS@MWCNT nano-aerogel shows superior EMW absorption property (cover all Ku-band) and thermal IR stealth property (ΔT reached 60.7 °C). Followed by a facial combination of the above nano-aerogel with graphene film of high electrical conductivity, an extremely high electromagnetic interference shielding material (66.5 dB, 2.06 mm thickness) with superior absorption performance of an average absorption-to-reflection (A/R) coefficient ratio of 25.4 and a low reflection bandwidth of 4.1 GHz (A/R ratio more than 10) was experimentally obtained in this work.

Flexible, Thermally Stable, and Ultralightweight Polyimide-CNT Aerogel Composite Films for Energy Storage Applications.

Polyimide (PI) aerogels are promising in various fields of application, ranging from thermal insulators to aerospace. However, they are typically in the form of a bulk monolith, which suffers from a lack of conformability and drapability. Moreover, their electrical conductivity is limited, and they mainly display an insulative behavior. These shortcomings can limit the applications of PI aerogels in energy storage systems, which require ultralightweight flexible conductive films, which at the same time offer high thermal stability, ultralow density, and high surface area. To overcome these obstacles, the present study reports the fabrication of PI-carbon nanotube (PI-CNT) aerogel composite films with varying CNT content prepared through a sol-gel preparation method, followed by a supercritical drying procedure. Compared to pristine PI aerogels, which displayed a large shrinkage and density of 18.3% and 0.12 g cm-3, respectively, the incorporation of only 5 wt % CNTs resulted in a significant reduction of both shrinkage and density to only 11.5% and 0.10 g cm-3, respectively. This suggests the importance of CNTs in improving the dimensional stability of aerogels and creating a robust network. Further characterizations showed that incorporation of 5 wt % CNTs also resulted in the highest pore volume (1.25 cm3 g-1), highest surface area (324 m2 g-1), highest real permittivity (80), highest electrical conductivity (3 × 10-1 S m-1), and ultrahigh service temperature (575 °C). It was also shown that the aerogel films can withstand a large degree of bending, can be twisted, and can be fully rolled with no obvious cracks propagated in the structure. The combined outstanding properties of the developed aerogel composite films make them promising potential candidates for supercapacitor electrodes. Therefore, the electrochemical performance of the devices based on aerogel electrodes was further studied. The device demonstrated a high energy density of 2.6 Wh kg-1 at a power density of 303.8 W kg-1. The total capacitance after 5000 cycles was 91.8% of the initial capacitance, which indicated excellent stability and durability of the device. Overall, this work provides a facile yet effective methodology for the development of high-performance aerogel materials for energy storage applications.

Layered polymer composite foams for broadband ultra-low reflectance EMI shielding: a computationally guided fabrication approach.

The development of layered polymer composites and foams offers a promising solution for achieving effective electromagnetic interference (EMI) shielding while minimizing secondary electromagnetic pollution. However, the current fabrication process is largely based on trial and error, with limited focus on optimizing geometry and microstructure. This often results in suboptimal electromagnetic wave reflection and the use of unnecessarily thick samples. In this study, an input impedance model was employed to guide the fabrication of layered PVDF composite foams. This approach optimized the void fraction (VF) and the thickness of each layer to achieve broadband low reflection. Moreover, hybrid heterostructures of SiCnw@MXene were incorporated into the PVDF composite foams as an absorption layer, while the conductive PVDF/CNT composite foams served as a shielding layer. Directed by theoretical computations, we found that combining 2.2 mm of PVDF/SiCnw@MXene composite foam (50% VF) and 1.6 mm of PVDF/CNT composite yielded EMI shielding effectiveness of 45 dB, with an average reflectivity (R) of 0.03 and an effective absorption bandwidth of 5.54 GHz (for R < 0.1) over the Ku-band (12.4-18 GHz). Importantly, the corresponding peak R was only 0.000017. Our work showcases a theoretically guided approach for developing absorption-dominant EMI shielding materials with broadband ultra-low reflection, paving the way for cutting-edge applications.

Correction: From micro/nano structured isotactic polypropylene to a multifunctional low-density nanoporous medium.

[This corrects the article DOI: 10.1039/C6RA22607H.].

Synergism Effect between Nanofibrillation and Interface Tuning on the Stiffness-Toughness Balance of Rubber-Toughened Polymer Nanocomposites: A Multiscale Analysis.

As the design and scalable technology development of tough, yet stiff, polymer nanocomposites receive attention in the automotive industry, fundamental understating of underlying toughening mechanisms at the nanoscale is inevitable. However, mechanical tests on rubber-toughened nanocomposites have shown that their overall fracture properties are significantly smaller than theoretical predictions. Our previous study showed that major factors in this regard are the simultaneous operation of different toughening mechanisms and the nanostructural features of the interface. As a result, it may be necessary to employ multiscale and multimechanism modeling strategies to accurately account for the contribution of each toughening mechanism. In this study, the effects of nanofibrillation (i.e., size, orientation, and dispersion) and interfacial tuning on the mechanical properties of nanofibrillated rubber-toughened nanocomposites are examined using molecular dynamics (MD) simulations. We report that by interfacial modification via grafting compatibilizer at the interface, nanofibrillated rubber-toughened polypropylene (PP) nanocomposite can achieve superior mechanical properties as a result of enhanced interfacial load transfer. Compared to pure ethylene propylene diene monomer rubber (EPDM)/PP system, an increase of 49% in energy absorbed per unit volume during fracture was achieved for 30% functionalized nanocomposites. Such an increase in energy dissipation was caused by a transition in the dominant crack propagation mechanism from interfacial slippage to crack-arresting behavior, owing to enhanced interfacial adhesion. MD simulations in conjunction with the multiscale model revealed that such a change in mechanism is caused by the formation of strong covalent bonds, interfacial friction, and the presence of a highly entangled polymeric network at the interface. Although the multiscale framework can be viewed as a road map for modeling the interface of various nanocomposite systems, the results obtained from our study may offer valuable insights for developing robust and scalable fabrication processes for nanofibrillated rubber-toughened nanocomposite structures, which pose significant technological challenges.

Enhanced electrical properties of microcellular polymer nanocomposites via nanocarbon geometrical alteration: a comparison of graphene nanoribbons and their parent multiwalled carbon nanotubes.

Geometric factors of nanofillers considerably govern the properties of conductive polymer composites (CPCs). This study provides insights into how geometrical alteration through nanotube-to-nanoribbon conversion affects the electrical properties of solid and microcellular CPCs. In this regard, polyvinylidene fluoride (PVDF)-based nanocomposites are synthesized using both the parent multi-walled carbon nanotube (MWCNT) and its chemically unzipped product, i.e., graphene nanoribbons (GNRs). Theoretical and experimental results show that GNR-based composites exhibit 1-4 orders greater conductivities than MWCNT-based composites at the same filler loading because of the larger number of filler-filler junctions as well as the significantly greater contact areas. On the other hand, the conductivities of MWCNT-based and GNR-based composites are significantly increased by 230 times and 121 times, respectively, through microcellular foaming. The effective rearrangements of rigid MWCNTs and flexible GNRs (having 4 and 5 orders less bending stiffness) for network formation during cellular growth are compared. The GNR-based composites also exhibit a superior dielectric permittivity (e.g., 2.6 times larger real permittivity at a representative frequency of 103 Hz and a nanofiller loading of 4.2 vol%) compared to their MWCNT-based counterparts. This study demonstrates how the modification of the carbon fillers and the polymer matrix can dramatically enhance EMI shielding.

Microscopic revelation of the solid-gas coupling and Knudsen effect on the thermal conductivity of silica aerogel with inter-connected pores.

As a star insulation material, aerogel plays a significant role in saving energy and meeting temperature requirements in industry due to its extremely low thermal conductivity. The prediction of aerogel's thermal conductivity is of great interest in both research and industry, particularly because of the difficulty in measuring the separated gas conductivities directly by experiment. Hence, the proportions of separated gas conduction and solid-gas coupling conduction are debatable. In this work, molecular dynamics simulations were performed on porous silica aerogel systems to determine their thermal conductivities directly. The pore size achieved in the present study was improved significantly, making it possible to include the gas phase in the investigation of aerogel thermal conductivity. The separated solid conductivity [Formula: see text] and the separated gas thermal conductivity [Formula: see text] as well as the effective solid conductivity [Formula: see text] and the effective gas conductivity [Formula: see text] were calculated. The results suggest that the solid-gas coupling effect is negligible in rarefied gas because the enhancement of thermal conduction due to the short cut bridging effect by gas between gaps in the solid is limited. The gas pressure is the most significant factor that affects the solid-gas coupling effect. The large differential between the prediction and the actual value of the thermal conductivity is mainly from the underestimate of [Formula: see text], and not because of ignoring the coupling effect. As a conclusion, the solid-gas coupling effect can be neglected in the prediction of silica aerogel's thermal conductivity at low and moderate gas pressure, i.e., decreasing the gas pressure is the most efficient way to suppress the coupling effect. The findings could be used in multi-scale simulations and be beneficial for improving the accuracy of predictions of aerogel thermal conductivity.

Mechanical Properties of Injection Molded PP/PET-Nanofibril Composites and Foams.

The creation and application of PET nanofibrils for PP composite reinforcement were studied. PET nanofibrils were fibrillated within a PP matrix using a spunbond process and then injection molded to test for the end-use properties. The nanofibril reinforcement helped to provide higher tensile and flexural performance in solid (unfoamed) injection molded parts. With foam injection molding, the nanofibrils also helped to improve and refine the microcellular morphology, which led to improved performance. Easily and effectively increasing the strength of a polymeric composite is a goal for many research endeavors. By creating nanoscale fibrils within the matrix itself, effective bonding and dispersion have already been achieved, overcoming the common pitfalls of fiber reinforcement. As blends of PP and PET are drawn in a spunbond system, the PET domains are stretched into nanoscale fibrils. By adapting the spunbonded blends for use in injection molding, both solid and foamed nanocomposites are created. The injection molded nanocomposites achieved increased in both tensile and flexural strength. The solid and foamed tensile strength increased by 50 and 100%, respectively. In addition, both the solid and foamed flexural strength increased by 100%. These increases in strength are attributed to effective PET nanofibril reinforcement.

Controlling stereocomplex crystal morphology in poly(lactide) through chain alignment.

The incorporation of poly(d-lactide) (PDLA) to form stereocomplex crystallites (SCs) within a poly(l-lactide) (PLLA) matrix is among the most effective strategies in overcoming PLLA's numerous drawbacks. However, high concentrations of PDLA (>3 wt%) are required to improve PLLA's crystallization kinetics and melt strength, which is undesirable owing to PDLA's high cost. In this study, we use chain alignment as a levier to tune stereocomplex superstructure morphology to overcome these limitations. Herein, PLLA/PDLA blends were manufactured using an environmentally friendly and low-cost single step spunbond fibrillation process, yielding microfibers stretched to diameters of 5-20 µm. During this stretching process, PLLA and PDLA chains are aligned along the flow direction. SCs subsequently formed in situ upon heating, dramatically improving crystallization kinetics, melt elasticity, and tensile performance compared with neat PLLA and non-stretched blend analogues, even with low PDLA content (<3 wt%). These improvements were attributed to topological variations in SC superstructures caused by alignment of PLLA and PDLA chains. The application of chain alignment in tuning SC superstructure morphology is ubiquitous in fibrillation processes.

Biomimetic hydrophobic plastic foams with aligned channels for rapid oil absorption.

Although many oil absorption materials have been developed, it still remains a great challenge to achieve rapid absorption and efficient recovery. Over the past decade, research has focused on the development of freeze casting technology using water as a solvent. The materials prepared by this method have poor water resistance and are difficult to apply to oil absorption in aqueous environments. Here, an organic solvent freeze casting strategy is proposed to fabricate ultralight hydrophobic plastic foams with aligned channel structures. Through microscopy in situ observation, we revealed the growth morphology of ice crystals during directional freezing process. Moreover, aligned porous foams with various channel sizes are fabricated by regulating the cooling rate. We found that organic solvent-assisted freeze casting can enhance the hydrophobicity of the matrix material. These aligned porous foams exhibit excellent liquid absorption performance, with high absorption speed and large absorption capacity over a wide viscosity range. This approach has general applicability and can be used to tailor a wide variety of engineering plastic-based aligned porous foams, as long as they can dissolve in organic solvents.

Sectorization of Macromolecular Single Crystals Unveiled by Probing Shear Anisotropy.

Polymer single crystals continue to infiltrate emerging technologies such as flexible organic field-effect transistors because of their excellent translational symmetry and chemical purity. However, owing to the methodological challenges, direct imaging of the polymer chains folding direction resulting in sectorization of single crystals has rarely been investigated. Herein, we directly image the sectorization of polymer single crystals through anisotropic elastic deformation on the surface of macromolecular single crystals. A variant of friction force microscopy, in which the scanning direction of the probe tip is parallel with the cantilever axis, allows for high contrast imaging of the sectorization in polymer single crystals. The lateral deflection of the cantilever resulting from shear forces transverse to the scan direction shows a close connection with the in-plane components of the elastic tensor of the polymer single crystals, which is of a fundamentally different origin than the friction forces. This allows for fast, facile, and nondestructive characterization of the microstructure and in-plane elastic anisotropy of compliant crystalline materials such as polymers.

Greatly Enhanced Electromagnetic Interference Shielding Effectiveness and Mechanical Properties of Polyaniline-Grafted Ti3C2Tx MXene-PVDF Composites.

Nowadays, evolutions in wireless telecommunication industries, such as the emergence of complex 5G technology, occur together with massive development in portable electronics and wireless systems. This positive progress has come at the expense of significant electromagnetic interference (EMI) pollution, which requires the development of highly efficient shielding materials with low EM reflection. The manipulation of MXene surface functional groups and, subsequently, incorporation into engineered polymer matrices provide mechanisms to improve the electromechanical performance of conductive polymer composites (CPCs) and create a safe EM environment. Herein, Ti3C2Tx MXene nanoflakes were first synthesized and then, taking advantage of their abundant surface functional groups, polyaniline (PA) nanofibers were grafted onto the MXene surface via oxidant-free oxidative polymerization at two different MXene to monomer ratios. The electrical conductivity, EMI shielding effectiveness (SE), and mechanical properties of poly (vinylidene fluoride) (PVDF)-based CPCs at different nanomaterial loadings were then thoroughly investigated. A very low percolation threshold of 1.8 vol % and outstanding electrical conductivities of 0.23, 0.195, and 0.17 S/cm were obtained at 6.9 vol % loading for PVDF-MXene, PVDF-MX2AN1, and PVDF-MX1AN1, respectively. Compared to the pristine MXene composite, surface modification significantly enhanced the EMI SE of the PVDF-MX2AN1 and PVDF-MX1AN1 composites by 19.6 and 32.7%, respectively. The remarkable EMI SE enhancement of the modified nanoflakes was attributed to (i) the intercalation of PA nanofibers between MXene layers, resulting in better nanoflake exfoliation, (ii) a large amount of dipole and interfacial polarization dissipation by constructing capacitor-like structures between nanoflakes and polymer chains, and (iii) augmented EMI attenuation via conducting PA nanofibers. The surface modification of the MXene nanoflakes also enhanced the interfacial interactions between PVDF chains and nanoflakes, which resulted in an improved Young's modulus of the PVDF matrix by about 67 and 46% at 6.9 vol % loading for PVDF-MX2AN1 and PVDF-MX1AN1 composites, respectively.

Friction of Ti3C2Tx MXenes.

2D materials are well-known for their low-friction behavior by modifying the interfacial forces at atomic surfaces. Of the wide range of 2D materials, MXenes represent an emerging material class but their lubricating behavior has been scarcely investigated. Herein, the friction mechanisms of 2D Ti3C2Tx MXenes are demonstrated which are attributed to their surface terminations. We find that Ti3C2Tx MXenes do not exhibit the well-known frictional layer dependence of other 2D materials. Instead, the nanoscale lubricity of 2D MXenes is governed by the termination species resulting from synthesis. Annealing the MXenes demonstrate a 7% reduction in OH termination which translates to a 16-57% reduction of friction in agreement with DFT calculations. Finally, the stability of MXene flakes is demonstrated upon isolation from their aqueous environment. This work indicates that MXenes can provide sustainable lubricity at any thickness which makes them uniquely positioned among 2D material lubricants.

Closely Packed Conductive Droplets with Polygon-Like Patterns Confined at the Interface in Ternary Polymer Blends.

This work reports on the formation of closely packed conductive droplets demonstrating polygon-like patterns at the interface in partially wetted ternary polymer systems prepared by melt blending and annealing treatment. The low-density polyethylene/poly(ether-block-amide)/poly(butylene-adipate-co-terephthalate) (LDPE/PEBA/PBAT) blend showed an intermediate partial wetting tendency where the interfacially localized conductive PEBA phase developed connected structure after blending but transformed into dispersed droplets upon annealing. The coalescence of the PEBA droplets appeared to be initiated by the Rayleigh-type instability in the thin PBAT film separating PEBA. However, the intrinsic coalescence rate of the PEBA droplets was very low due to the low interfacial tension of PEBA/PBAT. This slow coalescence of PEBA combined with the fast reduction in the interfacial area during annealing and the intermediate partial wetting state of the LDPE/PEBA/PBAT system resulted in a unique morphology of closely packed PEBA droplets with polygon-like patterns at a volume fraction of 50/10/40. Two other representative ternary polymer blends, LDPE/PEBA/polypropylene (PP) and compatibilized LDPE/PEBA/polystyrene (PS), with strong and weak partial wetting morphologies were also examined to highlight the mechanism for the morphology development in the LDPE/PEBA/PBAT blend.

Low-emission and energetically efficient co-gasification of coal by incorporating plastic waste: A modeling study.

The issues of global plastic waste generation and demand for hydrogen energy can be simultaneously resolved by gasification process. In this regard, feasibility and efficiency of steam and air co-gasification of coal by incorporating five different and prevalent types of plastic waste were investigated in this modeling study. All steam and air coal/plastic waste co-gasification types were multi-objective optimized utilizing a response surface methodology. The best co-gasification types were selected using VIekriterijumsko KOmpromisno Rangiranje (VIKOR) analysis. Overall, the results showed that incorporating plastic waste into coal gasification improved hydrogen concentration in the syngas and increased normalized carbon dioxide production due to the high carbon content of plastic waste and activation of water-gas and CO shift reactions. VIKOR analysis revealed that steam coal/low density polyethylene was the best optimized co-gasification type with hydrogen concentration of 62.8 mol %, normalized carbon dioxide production of 2.60 g/mol, based on the feedstock entering the system, and energy efficiency of 76.6%. Increasing gasifier temperature enhanced hydrogen concentration and decreased normalized carbon dioxide production. The energy efficiency was markedly improved by increasing the moisture content and decreasing the ratio of steam/feedstock. This study confirmed the hypothesis of efficient utilization of plastic waste in coal/plastic waste co-gasification.